Three Congolese polling stations were attacked with explosives early today, UN and election body sources said, hours after President Joseph Kabila urged voters to back a new constitution in a referendum tomorrow.
The stations were all schools where thousands were due to cast their ballots in the country's first national democratic vote in more than four decades.
The referendum is designed to approve a new postwar constitution to govern a series of elections and install a new government by the end of June.
"Three election offices were attacked here in Kinshasa early this morning," a UN official said after visiting the schools.
"One was blown up and everything destroyed, two others were attacked with molotov cocktails."
"We are carrying out investigations to find out who was responsible," said Dieudonne Mirimo, a spokesman for the Independent Electoral Commission.
The headmistress of one school, where about 2,000 were registed to vote, said classroom chairs and tables were burnt. "At about 3am the guards heard an explosion and then saw a fire," said headmistress Marie-Jeanne Ngwanda.
"All the material from my school and the election commission has been destroyed."
Opponents of the power-sharing interim government that includes former rebels have urged people to vote against the constitution, a move diplomats and Mr Kabila say would force the renegotiation of a peace deal and a 2-year-old transition process in the Democratic Republic of Congo.